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    <meta charset="UTF-8" />
    <title>Document</title>
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    <div>
      <h1>FLow函数类型</h1>
      <p>参数类型和返回值类型</p>
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    <script>
      //void哪里表示的是返回值
      function foo(callback: (string, number) => void) {
        callback("string", 100);
      }
      foo(function (str, n) {});
    </script>
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